sqlalchemy polymorphic load_only

gistfile1.py

# no
query = session.query(MySubModel)
query = query.options(load_only("id", "type"))

# yes, but does not filter type of model
query = session.query(MyModel).with_polymorphic(MySubModel)
query = query.options(load_only("id", "type"))

# yes, but ew
query = session.query(MyModel)
query = query.options(load_only("id", "type"))
query = query.filter(MyModel.type == "my_sub_model")

models.py

MyModel(Base):
    __table_name__ = "my_table"
    id = Column(Int, primary_key=True)
    name = Column(Text)
    type = Column(Text)
    __mapper_args__ = {'polymorphic_identity': 'my_model',
                       'polymorphic_on': type}

MySubModel(MyModel):
    __mapper_args__ = {'polymorphic_identity': 'my_sub_model'}